Case of the Month #27 - rhabdomyolysis
What is rhabdomyolysis and what are the causes?
Rhabdomyolysis results from breakdown of skeletal muscle and the consequent release of myocyte intracellular contents into the circulation. This includes electrolytes, myoglobin and proteins such as creatine kinase (CK), lactate dehydrogenase, alanine aminotransferase, and aspartate amino- transferase.
Muscle breakdown can occur in the context of direct muscle injury in cases such as trauma or depletion of ATP within the myocyte. This then leads to an unregulated increase in intracellular calcium. Muscle cells in health, have low sarcoplasmic levels of calcium at rest, the balance of which is maintained by cellular ATP pumps. Impairment of these pumps due to a lack of ATP leads to unregulated muscle contraction, high intra-myocyte calcium and a cascade of enzyme release that result in myocyte breakdown.
The causes of rhabdomyolysis are listed in the table below (adapted from reference 1):
|Physical exertion||Exercise Seizures|
|Hypoxic muscle injury||Major arterial occlusion Immobilsation Compartment Syndrome|
|Genetic||Disorders of glycolysis Disorders of glycogenolysis Lipid metabolism disorders Mitochondrial disorders|
|Infective||Influenza sp, Ebstein Barr Virus, Staph aureas, Strep pyogenes, legionella sp|
|Metabolic||Diabetes ketoacidosis, Non-ketotic hyperosmolar state, hyokalaemia, hypocalcaemia, hypophosphataemia|
|Drugs||Statins, Fibrates Alcohol, Cocaine, Heroin|
|Body temperature changes||Malignant Hyperthermia Neuroleptic malignant syndrome Heat Stroke|
In this case there are a number of risk factors present including muscle hypoxia secondary to prolonged immobility, moderate to heavy alcohol consumption, regular statin use and legionella pneumonia.
The clinical condition ranges from asymptomatic to life- threatening, with associated hyperkalaemia and acute kidney injury (AKI). Between 10 – 65% of patients with rhabdomyolysis develop acute kidney injury (AKI) and those with severe rhabdomyolysis-induced AKI have a mortality of approximately 20%2.